1. Field of the Invention
The present invention relates to the preparation of pigmentary grade quinacridone from preground quinacridone by aqueous ball milling.
2. Prior Art
U.S. Pat. No. 3,752,688 discloses grinding pigments in an alkaline aqueous medium to reduce the particle size of the pigment.
U.S. Pat. No. 4,158,572 discloses dry milling a phthalocyanine crude to reduce its particle size followed by stirring the pigment in an aqueous medium containing a surfactant.